Retroviral infections of small animals.

Retroviral infections are particularly important in cats, which are commonly infected with feline leukemia virus and feline immunodeficiency virus. This article describes the biology of these viruses and explores current issues regarding vaccination and diagnosis. The seeming lack of a recognized retrovirus infection in dogs is speculated on, and current and potential future therapies are discussed.     

Effects of aneuploidy on cellular physiology and cell division in haploid yeast

Aneuploidy is a condition frequently found in tumor cells, but its effect on cellular physiology is not known. We have characterized one aspect of aneuploidy: the gain of extra chromosomes. We created a collection of haploid yeast strains that each bear an extra copy of one or more of almost all of the yeast chromosomes. Their characterization revealed that aneuploid strains share a number of phenotypes, including defects in cell cycle progression, increased glucose uptake, and increased sensitivity to conditions interfering with protein synthesis and protein folding. These phenotypes were observed only in strains carrying additional yeast genes, which indicates that they reflect the consequences of additional protein production as well as the resulting imbalances in cellular protein composition. We conclude that aneuploidy causes not only a proliferative disadvantage but also a set of phenotypes that is independent of the identity of the individual extra chromosomes.     

Utilization of Transgenic Fish in Developing Countries: Potential Benefits and Risks

Recombinant DNA and gene transfer technology now allow the transfer, inheritance and expression of specific DNA or gene sequences into fish. Preliminary results on the performance of the resulting transgenic fish have been quite dramatic in some cases, especially when growth hormone genes are transferred. Utilization of high performance transgenic fish has the potential to greatly increase aquaculture production in developing countries and increase the income of poor farmers. Growth of some transgenic fish has been increased more than 10-fold in laboratory conditions. Response appears to be greatest in unimproved fish, which in most cases would benefit developing countries the most. The potential increase in production and production efficiency from successful transgenic fish application could relieve pressure on habitat destruction for food production, relieve pressure on overfished natural stocks and discourage introduction of exotic species. Application of transgenic fish in aquaculture has just begun and could expand within a few years. However, prior to commercialization of transgenic fish, public education, environmental risks and food safety issues should be addressed. Genetically improved fish generated by recombinant DNA technology probably do not pose any greater risk to the environment than fish genetically improved through traditional selective breeding, but environmental risk data is lacking to verify this hypothesis. Environmental risk data will be needed in a case-by-case basis until more is known concerning the aquaculture potential and ecological risk of transgenic fish. Research institutions need to address the lack of environmental risk data to help ensure that any future application of transgenic fish in developing (and developed) countries be done in an environmentally and socioeconomically sound manner. Socioeconomic study is lacking for detailed cost-benefit analysis, and policy research is needed for proper application or regulation of transgenic fish in these countries.     

Metapopulations and salmonids: a synthesis of life history patterns and empirical observations

Abstract – Metapopulation theory has attracted considerable interest with reference to the salmonids. There has been little empirical evidence, however, to guide the evaluation or application of metapopulation concepts. From knowledge of salmonid life histories and our own work with bull trout ( Salvelinus confluentus ), Lahontan cutthroat trout ( Oncorhynchus clarki henshawi ) and westslope cutthroat trout ( Oncorhynchus clarki lewisi ), we suggest that simple generalizations of salmonid metapopulations are inappropriate. Although spatial structuring and dispersal mechanisms are evident, the relevance of extinction and colonization processes are likely to vary with life history, species, scale, and landscape. Understanding dispersal, the role of suitable but unoccupied habitats, and the potential for extinction debts in non-equilibrium metapopulations are key issues. With regard to conservation of salmonids, we suggest that efforts to understand and conserve key processes likely to influence the persistence of populations or metapopulations will be more successful than efforts to design minimal habitat reserves based on metapopulation theory. ^NOTE     

Cytokines and anti-cytokine therapy: clinical potential for treatment of feline disease

Cytokines are soluble proteins produced by nucleated cells throughout the body. They have wide ranging effects on cell growth and differentiation, mediating immune responses, haemopoiesis and tissue repair. Advances in recombinant DNA technology have led to a vast increase in knowledge of their biological properties and subsequently their use in human clinical trials. The use of human cytokines in feline medicine has been of limited success as the action of cytokines is often species restricted or their activity may be neutralized due to antibody formation. Recently, however, many feline cytokines have been cloned which raises the possibility of their future use in the management and prevention of feline disease. Ultimately, they may find widespread clinical uses including the treatment of cancer, cytopenias and viral infections and as vaccine adjuvants.     

Variation in mineral micronutrient concentrations in grain of wheat lines of diverse origin

150 lines of bread wheat representing diverse origin and 25 lines of durum, spelt, einkorn and emmer wheat species were analysed for variation in micronutrient concentrations in grain. A subset of 26 bread wheat lines was grown at six sites or seasons to identify genetically determined differences in micronutrient concentrations. Substantial variation among the 175 lines existed in grain Fe, Zn and Se concentrations. Spelt, einkorn and emmer wheats appeared to contain higher Se concentration in grain than bread and durum wheats. Significant differences between bread wheat genotypes were found for grain Fe and Zn, but not Se concentration; the latter was influenced more by the soil supply. Grain Zn, but not Fe, concentration correlated negatively with grain yield, and there was a significant decreasing trend in grain Zn concentration with the date of variety release, suggesting that genetic improvement in yield has resulted in a dilution of Zn concentration in grain. Both grain Zn and Fe concentrations also correlated positively and significantly with grain protein content and P concentration, but the correlations with kernel size, kernel weight or bran yield were weak. The results from this study are useful for developing micronutrient biofortification strategies.     

Three-dimensional simulations of plume-lithosphere interaction at the hawaiian swell

Rapid lithospheric thinning by mantle plumes has not been achieved in numerical experiments performed to date. Efficient thinning depends on small-scale instabilities that convectively remove lithospheric material. These instabilities are favored by hotter plumes or stronger temperature dependence of viscosity, and a simple scaling independent of rheology controls their onset. This scaling allows extrapolation of the results of numerical experiments to the Earth's mantle. Mantle plumes between 100 and 150 kelvins hotter than the background mantle should exhibit small-scale convective rolls aligned with the plate motion. The unusual variation in heat flow across the Hawaiian swell may be due to such instabilities. It was found that the spreading of the plume creates a downwelling curtain of material that isolates it from the rest of the mantle for distances of at least 1000 kilometers from the plume origin. This isolation has important consequences for the geochemical heterogeneity of the lithosphere and upper mantle.     

Effects of Varying Dietary Protein Levels and Feeding Frequencies on Condition and Reproductive Performance of Channel Catfish to Produce Hybrid Catfish

The interspecific hybridization of channel catfish, Ictalurus punctatus, females with blue catfish, I. furcatus, males has been identified as a method to further improve production; however, lack of spawning success has affected its commercial application. To facilitate our understanding of the interaction of brood stock nutrition and reproductive performance, we evaluated the interaction of feed quality and feeding frequency. Channel catfish females were classified into two genetic groups, namely, high and low spawning. The treatments were offered during the spring season 70–90 d prior to the start of the spawning season. Induced reproduction was performed using luteinizing hormone releasing hormone analog. Condition of the fish as well as reproductive performance using spawning success, egg production, egg size, and fertilization at 48 h were determined. Changing protein level of the diet from 32 to 42% did not influence spawning, fecundity, or fertilization, but affected egg size and biochemical composition of the eggs. Increasing the feeding frequency from three to six times per week negatively affected spawning in one of the two genetics groups, did not affect egg production and egg fertilization, but had a significant effect on egg size. Older fish performed better than younger fish in terms of spawning success and egg production.